Lithographic apparatus and device manufacturing method

ABSTRACT

A lithographic apparatus includes a device having a blade selectively insertable into the beam. The device is in a first plane intermediate a second plane conjugate to a plane of the substrate and a third plane conjugate to a pupil plane of the projection system. The blade may include a partially opaque blade and a solid blade or have a predetermined transmissibility pattern. The transmissibility may vary in a second direction perpendicular to the first direction in which the substrate and the patterning device are movable. In an illumination system including a field faceted mirror and a pupil faceted mirror, a reflecting blade is selectively insertable into the beam to reflect a portion of the beam to a beam dump that may be cooled to reduce a heat load. The reflecting element may have a coating that scatters the portion of radiation or changes the phase.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is continuation of co-pending U.S. application Ser. No.10/784,895, filed Feb. 24, 2004, entitled “LITHOGRAPHIC APPARATUS ANDDEVICE MANUFACTURING METHOD,” which is a continuation-in-part of U.S.application Ser. No. 10/388,766, filed Mar. 17, 2003 and now U.S. Pat.No. 6,771,352, entitled “LITHOGRAPHIC APPARATUS AND DEVICE MANUFACTURINGMETHOD,” which claims priority from European Application No. 02251933.4,filed Mar. 18, 2002, the entire contents of each being hereinincorporated by reference. This application also incorporates byreference U.S. application Ser. No. 10/379,999, filed Mar. 6, 2003 andnow U.S. Pat. No. 6,927,004, entitled “MASK FOR USE IN LITHOGRAPHY,METHOD OF MAKING A MASK, LITHOGRAPHIC APPARATUS, AND DEVICEMANUFACTURING METHOD,” and Ser. No. 10/157,033, filed May 30, 2002 andnow U.S. Pat. No. 6,737,662, entitled “LITHOGRAPHIC APPARATUS, DEVICEMANUFACTURING METHOD, DEVICE MANUFACTURED THEREBY, CONTROL SYSTEM,COMPUTER PROGRAM, AND COMPUTER PRODUCT.” This application incorporatesby reference U.S. Pat. No. 6,583,855, issued Jun. 24, 2003 and entitled“LITHOGRAPHIC APPARATUS, DEVICE MANUFACTURING METHOD, ANDDEVICE-MANUFACTURED THEREBY.”

BACKGROUND

1. Field of the Invention

The present invention relates to a lithographic projection apparatus anddevice manufacturing method.

2. Description of the Related Art

The term “patterning device” as here employed should be broadlyinterpreted as referring to device that can be used to endow an incomingradiation beam with a patterned cross-section, corresponding to apattern that is to be created in a target portion of the substrate. Theterm “light valve” can also be used in this context. Generally, thepattern will correspond to a particular functional layer in a devicebeing created in the target portion, such as an integrated circuit orother device (see below). An example of such a patterning device is amask. The concept of a mask is well known in lithography, and itincludes mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. Placementof such a mask in the radiation beam causes selective transmission (inthe case of a transmissive mask) or reflection (in the case of areflective mask) of the radiation impinging on the mask, according tothe pattern on the mask. In the case of a mask, the support willgenerally be a mask table, which ensures that the mask can be held at adesired position in the incoming radiation beam, and that it can bemoved relative to the beam if so desired.

Another example of a patterning device is a programmable mirror array.One example of such an array is a matrix-addressable surface having aviscoelastic control layer and a reflective surface. The basic principlebehind such an apparatus is that, for example, addressed areas of thereflective surface reflect incident light as diffracted light, whereasunaddressed areas reflect incident light as undiffracted light. Using anappropriate filter, the undiffracted light can be filtered out of thereflected beam, leaving only the diffracted light behind. In thismanner, the beam becomes patterned according to the addressing patternof the matrix-addressable surface. An alternative embodiment of aprogrammable mirror array employs a matrix arrangement of tiny mirrors,each of which can be individually tilted about an axis by applying asuitable localized electric field, or by employing piezoelectricactuators. Once again, the mirrors are matrix-addressable, such thataddressed mirrors will reflect an incoming radiation beam in a differentdirection to unaddressed mirrors. In this manner, the reflected beam ispatterned according to the addressing pattern of the matrix-addressablemirrors. The required matrix addressing can be performed using suitableelectronics. In both of the situations described above, the patterningdevice can include one or more programmable mirror arrays. Moreinformation on mirror arrays as here referred to can be seen, forexample, from U.S. Pat. Nos. 5,296,891 and 5,523,193, and PCTpublications WO 98/38597 and WO 98/33096. In the case of a programmablemirror array, the support structure may be embodied as a frame or table,for example, which may be fixed or movable as required.

Another example of a patterning device is a programmable LCD array. Anexample of such a construction is given in U.S. Pat. No. 5,229,872. Asabove, the support in this case may be embodied as a frame or table, forexample, which may be fixed or movable as required.

For purposes of simplicity, the rest of this text may, at certainlocations, specifically direct itself to examples involving a mask andmask table. However, the general principles discussed in such instancesshould be seen in the broader context of the patterning device as setforth above.

Lithographic projection apparatus can be used, for example, in themanufacture of integrated circuits (IC's). In such a case, thepatterning device may generate a circuit pattern corresponding to anindividual layer of the IC, and this pattern can be imaged onto a targetportion (e.g. including one or more dies) on a substrate (silicon wafer)that has been coated with a layer of radiation-sensitive material(resist). In general, a single wafer will contain a whole network ofadjacent target portions that are successively irradiated via theprojection system, one at a time. In current apparatus, employingpatterning by a mask on a mask table, a distinction can be made betweentwo different types of machine. In one type of lithographic projectionapparatus, each target portion is irradiated by exposing the entire maskpattern onto the target portion at once. Such an apparatus is commonlyreferred to as a wafer stepper. In an alternative apparatus, commonlyreferred to as a step-and-scan apparatus, each target portion isirradiated by progressively scanning the mask pattern under the beam ina given reference direction (the “scanning” direction) whilesynchronously scanning the substrate table parallel or anti-parallel tothis direction. Since, in general, the projection system will have amagnification factor M (generally <1), the speed V at which thesubstrate table is scanned will be a factor M times that at which themask table is scanned. More information with regard to lithographicdevices as here described can be seen, for example, from U.S. Pat. No.6,046,792.

In a known manufacturing process using a lithographic projectionapparatus, a pattern (e.g. in a mask) is imaged onto a substrate that isat least partially covered by a layer of radiation-sensitive material(resist). Prior to this imaging, the substrate may undergo variousprocedures, such as priming, resist coating and a soft bake. Afterexposure, the substrate may be subjected to other procedures, such as apost-exposure bake (PEB), development, a hard bake andmeasurement/inspection of the imaged features. This array of proceduresis used as a basis to pattern an individual layer of a device, e.g. anIC. Such a patterned layer may then undergo various processes such asetching, ion-implantation (doping), metallization, oxidation,chemo-mechanical polishing, etc., all intended to finish off anindividual layer. If several layers are required, then the wholeprocedure, or a variant thereof, will have to be repeated for each newlayer. It is important to ensure that the overlay juxtaposition) of thevarious stacked layers is as accurate as possible. For this purpose, asmall reference mark is provided at one or more positions on the wafer,thus defining the origin of a coordinate system on the wafer. Usingoptical and electronic devices in combination with the substrate holderpositioning device (referred to hereinafter as “alignment system”), thismark can then be relocated each time a new layer has to be juxtaposed onan existing layer, and can be used as an alignment reference.Eventually, an array of devices will be present on the substrate(wafer). These devices are then separated from one another by atechnique such as dicing or sawing, whence the individual devices can bemounted on a carrier, connected to pins, etc. Further informationregarding such processes can be obtained, for example, from the book“Microchip Fabrication: A Practical Guide to Semiconductor Processing”,Third Edition, by Peter van Zant, McGraw Hill Publishing Co., 1997, ISBN0-07-067250-4.

For the sake of simplicity, the projection system may hereinafter bereferred to as the “lens.” However, this term should be broadlyinterpreted as encompassing various types of projection system,including refractive optics, reflective optics, and catadioptricsystems, for example. The radiation system may also include componentsoperating according to any of these design types for directing, shapingor controlling the beam of radiation, and such components may also bereferred to below, collectively or singularly, as a “lens”. Further, thelithographic apparatus may be of a type having two or more substratetables (and/or two or more mask tables). In such “multiple stage”devices the additional tables may be used in parallel or preparatorysteps may be carried out on one or more tables while one or more othertables are being used for exposures. Dual stage lithographic apparatusare described, for example, in U.S. Pat. Nos. 5,969,441 and 6,262,796.

Correct imaging of a pattern generated by a patterning device in alithographic projection apparatus requires correct illumination of thepatterning device. In particular, it is important that the intensity ofillumination proximal the plane of the pattern, as generated by thepatterning device, or proximal planes conjugate to the plane of thepattern, be uniform over the area of the exposure field. Also, it isgenerally required that the patterning device can be illuminated withoff-axis illumination in a variety of modes such as, for example,annular, quadrupole or dipole illumination, to improve resolution. Theuse of such illumination modes is disclosed, for example, in U.S. Pat.No. 6,671,035. The illumination modes are obtained, for example, byproviding a corresponding predetermined intensity distribution in apupil of the illumination system.

To meet the above-mentioned requirements, the illumination system of alithographic projection system is generally quite complex. A typicalillumination system might include: shutters and attenuators configuredto control the intensity of the beam output by the source, which mightbe a high pressure Hg lamp or an excimer laser; a beam shaping elementsuch as, for example, a beam expander for use with an excimer laserradiation beam configured to lower the radiation beam divergence; azoomable axicon pair and a zoom lens configured to set the illuminationmode and parameters (collectively referred to as a zoom-axicon); anintegrator, such as a quartz rod, configured to make the intensitydistribution of the beam more uniform; masking blades configured todefine the illumination area; and imaging optics configured to projectan image of the exit of the integrator onto the patterning device. Forsimplicity, the plane of the pattern generated by the patterning device,and planes conjugate to this plane in the illumination system and theprojection system may be referred to hereinafter as “image” planes.

The illumination system may also include elements configured to correctnon-uniformities in the illumination beam at or near image planes. Forexample, the illumination system may include diffractive opticalelements to improve the match of the beam cross-section proximal theentrance face of the integrator rod with the shape of the entrance face.A diffractive optical element typically includes an array ofmicrolenses, which may be Fresnel lenses or Fresnel zone plates.Improving the match alleviates the problem of field dependentlithographic errors occurring in the patterned layer. The matching mayhereinafter be referred to as “filling” of the integrator entrance face.A diffractive optical element may also be positioned, for example, infront of a beam shaping element, such as a zoom-axicon, to transform theangular distribution of radiation provided by an excimer laser beam intoa predetermined angular distribution of radiation to generate a desiredillumination mode. Illumination systems as discussed above aredisclosed, for example, in U.S. Pat. Nos. 5,675,401 and 6,285,443.

The illumination system may also include, for example, a filterpartially transmissive to radiation of the beam with a predeterminedspatial distribution of transmittance, immediately before the plane ofthe pattern, to reduce spatial intensity variations.

The illumination systems discussed above still suffer from variousproblems, however. In particular, various elements that are used,especially diffractive optical elements and quartz-rod integrators, canintroduce an anomaly of intensity distribution in a plane perpendicularto the optical axis of the radiation system or the projection system.For example, in a plane proximal a pupil of the radiation system or theprojection system, either the beam cross-section may be ellipticalrather than circular, or the beam intensity distribution within the beamcross-section may, for example, be elliptically symmetric rather thancircularly symmetric. Both types of errors are referred to as“ellipticity of the beam” or simply as “ellipticity error,” andtypically lead to specific lithographic errors in the patterned layers.In particular, a patterned feature occurring in directions parallel toboth the X and Y direction may exhibit, in the presence of ellipticityof the beam, different sizes upon exposure and processing. Such alithographic error is usually referred to as H-V difference. Also, adiffractive optical element used to improve filling of the integrator isgenerally only optimum for one setting of the zoom-axicon. For othersettings, the integrator entrance face may be under-filled (the beamcross-section is smaller than the integrator entrance face), leading tosubstantial field dependent H-V difference. For other settings, theintegrator entrance face may also be over-filled, leading to energywastage. Additionally, 157 nm excimer lasers and other excimer laserstend to have large divergence differences in X and Y directions whichcannot be completely resolved using beam expander lenses while keepingthe shape of the beam within acceptable dimensions.

Ellipticity errors in the beam may also be caused by subsequentelements, such as the mask and elements of the projection system.Current lithographic apparatus do not correct or compensate forellipticity errors introduced into the beam by elements subsequent tothe illumination system.

In a lithographic apparatus, it is important that illumination of thepatterning device is uniform in field and angle distribution and, forillumination modes such as dipole and quadrupole illumination, all polesare equal. To achieve this, an integrator is provided in theillumination system. In a lithographic apparatus using UV or DUVexposure radiation the integrator may take the form of a quartz rod or aso-called fly's eye lens. A fly's eye lens is a lens built up of a largenumber of smaller lenses in an array which creates a correspondinglylarge number of images of the source in a pupil plane of theillumination system. These images act as a virtual, or secondary,source. However, when using EUV exposure radiation the illuminationsystem must be constructed from mirrors because there is no knownmaterial suitable for forming a refractive optical element for EUVradiation. In such an illumination system, a functional equivalent to afly's eye lens can be provided using faceted mirrors, for instance asdescribed in U.S. Pat. Nos. 6,195,201, 6,198,793 and 6,452,661. Thesedocuments describe a first, or field, faceted mirror which focuses aplurality of images, one per facet, on a second, or pupil, facetedmirror which directs the light to appropriately fill the pupil of theprojection system. It is known from UV and DUV lithography that imagingof different types of mask patterns can be improved by controlling theillumination settings, e.g. the filling ratio of the pupil of theprojection system (commonly referred to as a) or the provision ofspecial illumination modes such as annular, dipole or quadrupoleillumination. More information on illumination settings can be obtainedfrom U.S. Pat. No. 6,452,662 and U.S. Pat. No. 6,671,035.

In an EUV lithographic apparatus with a fly's eye integrator, theseillumination settings can be controlled by selectively blocking certainof the pupil facets. However, because the source position and size oneach facet is not exactly known and not stable, it is necessary to blockoff whole facets at a time, rather than partial facets. Thus, onlyrelatively coarse control of illumination settings is possible. Also, toprovide an annular illumination setting it is necessary to obscure theinnermost pupil facets and when positioning a masking blade over aninner facet it is difficult to avoid partially obscuring one or more ofthe outer facets.

Referring to FIGS. 14 a and 14 b, a pupil plane includes a plurality ofoverlapping pupils. The overlapping pupils produce a field plane. Asshown in FIGS. 14 a and 14 b, a square field plane is formed by fouroverlapping cones of radiation in the pupil plane. In the pupil plane,the pupil shape can be corrected for all field positions withtransmission filters. The pupil distribution cannot be influenced overthe field in a controlled manner. Only a pupil correction that isconstant over the field can be applied. In the field plane, theuniformity profile can be changed for all angles with transmissionfilters. Transmission filters can only change the transmission for allangles.

In order to make field dependent corrections to the pupil distribution,the correction must take place between the pupil plane and the fieldplane. The difficulty is that the pupil of one field point overlaps withthe pupil of an adjacent field point. In an intermediate plane, the leftportion of a pupil corresponding to a right field point overlaps withthe right portion of a pupil corresponding to a left field point.Accordingly, it is not possible to correct one portion of the pupil forone field point without affecting the pupil for another field point.

SUMMARY

According to an exemplary embodiment of the present invention, alithographic apparatus includes a radiation system configured to providea beam of radiation. The radiation system includes an illuminationsystem. A support is configured to support a patterning device and thepatterning device is configured to pattern the beam of radiationaccording to a desired pattern. A substrate table is configured to holda substrate. The apparatus also includes a projection system configuredto project the patterned beam of radiation onto a target portion of thesubstrate; and a device positioned in a first plane intermediate asecond plane conjugate to a plane of the substrate and a third planeconjugate to a pupil plane of the projection system. The device includesa plurality of blades. Each blade is selectively insertable into thebeam of radiation.

According to another aspect of the present invention a devicemanufacturing method includes providing a beam of radiation using aradiation system, the radiation system including an illumination system;using a patterning device to endow the beam of radiation with a patternin its cross-section; projecting the patterned beam of radiation onto atarget portion of a layer of radiation-sensitive material at leastpartially covering a substrate using a projection system; andselectively inserting at least one blade of a plurality of blades intothe beam of radiation in a first plane intermediate a second planeconjugate to a plane of the substrate and a third plane conjugate to apupil plane of the projection system.

According to still another aspect of the present invention, alithographic apparatus includes a radiation system configured to providea beam of radiation, the radiation system including an illuminationsystem, the illumination system including a field faceted mirror and apupil faceted mirror. A support is configured to support a patterningdevice and the patterning device is configured to pattern the beam ofradiation according to a desired pattern. A substrate table isconfigured to hold a substrate and a projection system is configured toproject the patterned beam of radiation onto a target portion of thesubstrate. A plurality of reflective blades are each selectivelyinsertable into the beam of radiation in front of at least one facet ofat least one of the field faceted mirror and the pupil faceted mirror toreflect a portion of the beam of radiation to a beam dump.

According to an even further aspect of the present invention, a devicemanufacturing method includes providing a beam of radiation using aradiation system, the radiation system including an illumination system,the illumination system including a field faceted mirror and a pupilfaceted mirror; using a patterning device to endow the beam of radiationwith a pattern in its cross-section; projecting the patterned beam ofradiation onto a target portion of a layer of radiation-sensitivematerial at least partially covering a substrate using a projectionsystem; and selectively inserting at least one reflective blade into thebeam of radiation in front of at least one facet of at least one of thefield faceted mirror and the pupil faceted mirror to reflect a portionof the beam of radiation to a beam dump.

Although specific reference may be made in this text to the use of theapparatus according to the invention in the manufacture of ICs, itshould be explicitly understood that such an apparatus has many otherpossible applications. For example, it may be employed in themanufacture of integrated optical systems, guidance and detectionpatterns for magnetic domain memories, liquid-crystal display panels,thin-film magnetic heads, etc. The skilled artisan will appreciate that,in the context of such alternative applications, any use of the terms“reticle”, “wafer” or “die” in this text should be considered as beingreplaced by the more general terms “mask”, “substrate” and “targetportion”, respectively.

In the present document, the terms “radiation” and “beam” are used toencompass all types of electromagnetic radiation, including ultravioletradiation (e.g. with a wavelength of 365, 248, 193, 157 or 126 nm) andextreme ultra-violet radiation (EUV), e.g. having a wavelength in therange 5-20 nm, especially around 13 nm, as well as particle beams, suchas ion beams or electron beams.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described, by way ofexample only, with reference to the accompanying schematic drawings inwhich:

FIG. 1 is a schematic illustration of a lithographic projectionapparatus according to an exemplary embodiment of the present invention;

FIG. 2 is a schematic illustration of a lithographic projectionapparatus according to an exemplary embodiment of the present invention;

FIG. 3 a is a schematic illustration of an illumination system accordingto an exemplary embodiment of the present invention;

FIG. 3 b is a schematic illustration of an illumination system accordingto another exemplary embodiment of the present invention;

FIG. 4 is a schematic illustration of an ellipticity correction deviceaccording to an exemplary embodiment of the present invention;

FIG. 5 is a further schematic illustration of the device of FIG. 4;

FIG. 6 is a schematic illustration of a portion of the device of FIGS. 4and 5;

7 a and 7 b are perspective and plan view schematic illustrations,respectively, of a radiation beam;

FIG. 8 is a schematic illustration of a device according to anotherexemplary embodiment of the present invention;

FIGS. 9 a-9 c are schematic illustrations of the operation of a step andscan lithographic apparatus according to an exemplary embodiment of thepresent invention;

FIG. 10 is a schematic illustration of an effective or total pupil spotas seen by a wafer in a step and scan lithographic apparatus accordingto FIGS. 9 a-9 c;

FIG. 11 is a schematic illustration of an illumination system accordingto an exemplary embodiment of the present invention;

FIG. 12 a is a schematic illustration of an illumination systemaccording to an yet another exemplary embodiment of the presentinvention;

FIG. 12 b is a schematic illustration of the illumination system of FIG.12 a in a different configuration;

FIG. 13 a is a schematic illustration of an illumination systemaccording to a still further exemplary embodiment of the presentinvention;

FIG. 13 b is a schematic illustration of the illumination system of FIG.13 a in a different configuration; and

FIGS. 14 a and 14 b are schematic illustrations of a radiation beam ofan illumination system of a step and scan lithographic apparatus;

FIG. 15 depicts certain components of the illumination system of theapparatus of FIG. 1;

FIGS. 16 to 18 depict the facet masking means of the first embodiment ofthe invention in various positions;

FIG. 19 depicts a partially opaque masking blade used in the firstembodiment of the invention;

FIG. 20 depicts a partially opaque masking blade in accordance with thefirst embodiment of the present invention;

FIG. 21 depicts certain components of the illumination system of asecond embodiment of the invention; and

FIG. 22 depicts the field facet mirror of the second embodiment of theinvention.

In the Figures, corresponding reference symbols indicate correspondingparts.

DETAILED DESCRIPTION

FIG. 1 schematically depicts a lithographic projection apparatus 1according to an embodiment of the invention. The apparatus 1 includes abase plate BP. A illumination system is configured to supply a beam PBof radiation (e.g. EUV radiation). A radiation source SO is configuredto provide radiation to the illumination system IL. The source SO andthe apparatus 1 may be separate, for example when the source is a plasmadischarge source. In such case, the source SO is not considered to formpart of the apparatus 1 and the radiation beam is generally passed fromthe source LA to the illumination system IL with the aid of a radiationcollector including, for example, suitable collecting mirrors and/or aspectral purity filter. In other cases, the source SO may be integralwith the apparatus 1, for example when the source SO is a mercury lamp.The present invention encompasses both of these scenarios. The source SOand the illumination system IL may be referred to as a radiation system.

A first object (mask) table MT provided with a mask holder is configuredto hold a mask MA (e.g. a reticle), and is connected to a firstpositioning device PM configured to accurately position the mask withrespect to a projection system or lens PL. A second object (substrate)table WT provided with a substrate holder is configured to hold asubstrate W (e.g. a resist-coated silicon wafer), and is connected to asecond positioning device PW configured to accurately position thesubstrate with respect to the projection system PL. The projectionsystem or lens PL (e.g. a mirror group) is configured to image anirradiated portion of the mask MA onto a target portion C (e.g.comprising one or more dies) of the substrate W.

As here depicted, the apparatus is of a reflective type (i.e. has areflective mask). However, in general, it may also be of a transmissivetype, for example with a transmissive mask. Alternatively, the apparatusmay employ another kind of patterning device, such as a programmablemirror array of a type as referred to above.

The source SO (e.g. a discharge or laser-produced plasma source)produces radiation. The radiation is fed into the illumination systemIL, either directly or after having traversed a conditioning device,such as a beam expander Ex, for example. The illumination system IL mayinclude an adjusting device AM that sets the outer and/or inner radialextent (commonly referred to as σ-outer and σ-inner, respectively) ofthe angular intensity distribution in the radiation beam. In addition,it will generally include various other components, such as anintegrator IN and a condenser CO. In this way, the beam PB impinging onthe mask MA has a desired uniformity and intensity distribution in itscross-section.

The beam PB subsequently intercepts the mask MA, which is held on a masktable MT. Having traversed the mask MA, the beam PB passes through thelens PL, which focuses the beam PB onto a target portion C of thesubstrate W. With the aid of the second positioning device PW andinterferometer IF, the substrate table WT can be moved accurately, e.g.so as to position different target portions C in the path of the beamPB. Similarly, the first positioning device PM can be used to accuratelyposition the mask MA with respect to the path of the beam PB, e.g. aftermechanical retrieval of the mask MA from a mask library, or during ascan. In general, movement of the object tables MT, WT will be realizedwith the aid of a long-stroke module (coarse positioning) and ashort-stroke module (fine positioning), which are not explicitlydepicted in FIG. 1. However, in the case of a wafer stepper (as opposedto a step and scan apparatus) the mask table MT may just be connected toa short stroke actuator, or may be fixed. The mask MA and the substrateW may be aligned using mask alignment marks M₁, M₂ and substratealignment marks P₁, P₂.

The depicted apparatus can be used in two different modes:

1. In step mode, the mask table MT is kept essentially stationary, andan entire mask image is projected at once, i.e. a single “flash,” onto atarget portion C. The substrate table WT is then shifted in the X and/orY directions so that a different target portion C can be irradiated bythe beam PB;

2. In scan mode, essentially the same scenario applies, except that agiven target portion C is not exposed in a single “flash.” Instead, themask table MT is movable in a given direction (the so-called “scandirection”, e.g., the Y direction) with a speed v, so that the beam PBis caused to scan over a mask image. Concurrently, the substrate tableWT is simultaneously moved in the same or opposite direction at a speedV=Mv, in which M is the magnification of the lens PL (typically, M=¼ or⅕). In this manner, a relatively large target portion C can be exposed,without having to compromise on resolution.

FIG. 2 shows the projection apparatus 1 according to an exemplaryembodiment including the illumination system IL, the source SO, and theprojection system PL. The source SO includes a source collector moduleor radiation unit 3. The illumination system IL includes an illuminationoptics unit 4. A radiation system 2 includes the source-collector moduleor radiation unit 3 and the illumination optics unit 4. The radiationunit 3 is provided with the radiation source SO which may be formed by adischarge plasma. An EUV. radiation source may employ a gas or vapor,such as Xe gas or Li vapor in which a very hot plasma may be created toemit radiation in the EUV range of the electromagnetic spectrum. Thevery hot plasma is created by causing a partially ionized plasma of anelectrical discharge to collapse onto the optical axis O. The radiationemitted by radiation source SO is passed from a source chamber 7 into acollector chamber 8 via a gas barrier structure or “foil trap” 9. Thegas barrier structure 9 includes a channel structure such as, forexample, described in U.S. Pat. No. 6,359,969. The collector chamber 8includes a radiation collector 10, which may be formed by a grazingincidence collector. Radiation passed by the collector 10 is reflectedoff a grating spectral filter 11 to be focused in a virtual source point12 at an aperture in the collector chamber 8. From the collector chamber8, the radiation beam is directed to the illumination optics unit 4.

The illumination optics unit 4 includes a field faceted mirror 13including a plurality of field facets (not shown) and a pupil facetmirror 14 including a plurality of pupil facets 120 (FIGS. 4 and 5). Inthe present embodiment, three mirrors 15 a, 15 b, 15 c magnify and shapethe beam 16 before it impinges on the mask on the mask table MT. Thepath of the beam 16 is shown in more detail in FIGS. 3 a and 3 b. Themirror 15 a may preferably be a toroidal mirror, the mirror 15 b maypreferably be a spherical mirror, and the mirror 15 c may preferably bea grazing incidence mirror. A patterned beam 17 is formed which isimaged in projection system PL via reflective elements 18, 19 onto thewafer on the substrate table WT. More elements than shown may generallybe present in illumination optics unit 4 and the projection system PL.

Referring to FIG. 4, there is a position along the beam trajectorybetween the pupil faceted mirror 14 and the mask where the cross-sectionof the beam 16 is substantially rectangular. The size of the beamcross-section at this position corresponds to the size of the fieldfacets of mirror 13. The cross-section of the beam at this position isblurred by a convolution with the pupil spot distribution and is thusnot in focus with respect to the field plane. As shown in FIGS. 3 a and3 b, the position is after the pupil faceted mirror 14 and in front ofone of the mirrors 15 a, 15 b, or 15 c, and preferably relatively closeto the field plane compared to the pupil plane. It should be appreciatedthat an ellipticity correction device 20 may be positioned other than asshown in the exemplary embodiments of FIGS. 3 a and 3 b.

As shown in FIG. 4, the position is in front of one of the mirrors 15 a,15 b, or 15 c and the actual size of the field plane at the position isshown by solid lines 100. The size of the field plane before convolutionwith the pupil spots 120 is shown by dashed lines 110. The cross-sectionof the beam at the position is substantially rectangular. Pupil spots120, including integrated pupil spots 125, are distributed throughoutthe cross section of the beam at the position. The device 20, includinga plurality of adjustable blades 22, 24 is provided at the position. Theblades 22, 24 are adjustable by linear actuators 23, 25 (FIG. 5) to beinserted into the beam in the Y direction. The position of the device 20is schematically illustrated in FIG. 3 a as prior to the mirror 15 a ina direction of propagation of the beam, but as discussed above thedevice 20 may be positioned in front of either mirror 15 b or 15 c. Thedevice 20 may be positioned anywhere between the pupil faceted mirror 14and the mask, such as shown in FIG. 3 b for example, but is preferablypositioned relatively close to the field plane in comparison to thepupil plane.

Referring to FIGS. 4 and 5, the positions of the blades 22, 24 areadjustable by the linear actuators 23, 25 to be insertable into the beam16 in the Y direction so that part of the pupil spots 120, 125 arecovered. The blades 22, 24 are adjusted so that only those pupil spots120, 125 that correspond to positions at the edge of the cross sectionof the beam 16 in the Y direction are covered. The amount of radiationincident under an angle in the Y direction, i.e. the “vertical light,”is decreased in those pupil spots 120, 125 that are covered, wholly orpartially. Thus, when a scan is performed the integrated vertical lightis less than the “horizontal light,” i.e., the radiation incident underan angle in the X direction. The device 20 corrects or compensates theellipticity value (the ratio of the vertical light to the horizontallight) of the beam at the position by taking into account theellipticity error(s) that may be introduced into the beam by subsequentelements of the illumination system, the mask, and/or the projectionsystem. The ellipticity value can be corrected or compensated bydecreasing the amount of vertical light only. By absorbing or blockingvertical light at selected positions in the X direction, the totalamount of light decreases and the uniformity, i.e. intensity variationover the cross section of the beam, is corrected or compensated. Thevariation may be corrected by an apparatus such as the one disclosed inU.S. Pat. No. 6,404,499, for example.

Referring to FIG. 5, the device 20 includes partially opaque blades 22and solid blades 24 connected to respective linear actuators 23 and 25so as to be selectively and incrementally insertable into the beam inthe Y direction. The blades 22 and 24 may also be reflective. The bladesmay have a reflection profile that varies from completely reflecting tofully absorbing. The blades 22 and 24 are constructed as a plurality offingers 26 and 27, one of each per column of field or pupil facets thatare selectively and incrementally extendible to cover ones of the fieldor pupil facets. However, it should be appreciated that pairs or groupsof fingers may be grouped together.

The partially opaque fingers may be constructed, for example, as a gridof rods, bars or wires or by forming apertures in a suitable pattern ina solid plate. A partially opaque finger 26 formed with a plurality ofrods 29 is shown in FIG. 6.

In general, for other shapes and arrangements of pupil spots, the blades22 and 24 may be arranged differently. As an alternative to adjustableblades, it is possible to provide a plurality of blades, partiallyopaque, solid and/or reflecting, corresponding to desired illuminationsettings and selectively interpose these into the beam 16 as desired.Such fixed blades may be formed as plates with appropriate openings andpartially opaque (apertured) areas and may be held in a magazine orcarousel to be inserted into the beam.

By providing multiple partially opaque blades with different blockingratios, smaller increments of the pupil filling ratio a can be provided.For example, with two appropriately aligned partially opaque blades, oneblocking 25% and one blocking 50%, quarter steps can be provided. A stepis one row or column on the field or pupil facet mirror. For example, byextending the 25% blade one more step than a solid masking blade aquarter step is provided. Extending the 50% blade one step more providesa half step and both the 25% and 50% blade extended one more stepprovides a three quarter step.

Referring to FIGS. 7 a and 7 b, the field plane and the pupil plane fora beam in a step and scan lithographic apparatus are schematicallyillustrated. In an intermediate plane, there is a field-likedistribution in the X (non-scanning) direction and a pupil-likedistribution in the Y (scanning) direction. As in the exemplaryembodiment discussed above, it is possible to place a filter at theedges of the intermediate plane in the Y direction. To properly performa pupil compensation or correction, the compensation or correction mustbe done relatively far from the field plane. The correction orcompensation is preferably performed relatively far from the reticle. Ina step and scan apparatus, the beam cross section has a relatively smalldimension in the Y (scanning) direction and a relatively largerdimension in the X (non-scanning) direction. The beam cross section isthus pupil-like in the scanning (Y) direction relatively close to thefield plane and field-like in the non-scanning (X) direction. The pupilmay thus be corrected in the scanning direction by inserting filtershaving predetermined absorbing patterns into the intermediate plane inthe scanning (Y) direction.

Referring to FIG. 8, blades or plates 28 having predeterminedtransmissibility/absorbing patterns are insertable in the Y directioninto the edges of the intermediate plane to correct the ellipticityvalue. The blades 28 are insertable and adjustable by linear actuators21, similar to the embodiment described above. Thetransmissibility/absorbing pattern of the blades 28 may be formed toprovide a predetermined field dependence to the device 20A. As shown,the pattern of the blades 28 varies in the non-scanning (X) directionand thus the correction or compensation can vary in the non-scanningdirection.

Referring to FIGS. 9 a-c, in a step and scan lithographic apparatus 1,the pupil P as seen on the substrate W changes during a scan. Theilluminated area IA is defined as a sharp image of a quartz rodintegrator (discussed in more detail below). FIG. 9 a schematicallyillustrates the pupil P1 as seen by the substrate W immediately afterthe beginning of a scan. FIG. 9 b schematically illustrates the pupil P2as seen by the substrate W in the middle of a scan. FIG. 9 cschematically illustrates the pupil P3 as seen by the substrate Wimmediately prior to the end of a scan. Although the step and scanapparatus illustrated in FIGS. 9 a-c uses a transmissive mask, it shouldbe appreciated that the present invention also contemplates the use ofreflective masks.

Referring to FIG. 10, the sum of all the static pupils P1-P3 seen by thesubstrate results in the effective or scanning pupil P. Although threestatic pupils P1-P3 are schematically illustrated, it should beappreciated that during a scan a significantly larger number of staticpupils are summed to produce the effective or scanning pupil.

Referring to FIG. 11, an illumination system IL according to anotherexemplary embodiment of the present invention includes a radiationsource SO, for example a high pressure Hg lamp provided with anelliptical reflector to collect the output radiation or a laser. Twoshutters are provided to control the output of the lamp: a safetyshutter 111 held open by a coil 111 a and arranged to closeautomatically if any of the panels of a casing of the lithographicapparatus are opened. A rotary shutter 112 is driven by a motor 112 afor each exposure. A second rotary shutter 113 is driven by a motor 113a and a light attenuating filter in the shutter aperture may be providedfor low-dose exposures.

Beam shaping is principally performed by an axicon 115 and zoom lens116, which are adjustable optical elements driven by respective servosystems 115 a, 116 a. These components are referred to collectively asthe zoom-axicon. The axicon 115 includes a concave conical lens andcomplementary convex conical lens whose separation is adjustable.Setting the two elements of the axicon 115 together providesconventional circular illumination, while moving them apart creates anannular illumination distribution.

The zoom lens 116 determines the size of the beam or the outer radius ofan annular illumination mode. A pupil shaping device (not shown) may beinserted, for instance, in the exit pupil 122 of the zoom-axicon moduleto provide quadrupole or other illumination modes. Coupling opticscouple the light from the zoom-axicon into an integrator IN.

The integrator IN includes, for example two elongate quartz rods 117joined at a right-angle prism 117 a, the hypotenuse surface of which ispartially silvered to allow a small, known proportion of the beam energythrough to an energy sensor ES. The beam undergoes multiple internalreflections in the quartz rods 117 so that, looking back through it,there is seen a plurality of spaced apart virtual sources, thus eveningout the intensity distribution of the beam. It should be appreciatedthat a fly's eye lens could be used as the integrator.

After the exit of the integrator IN the device 20A is positioned tocorrect or compensate for the ellipticity value of the illumination areaIA, i.e. the area of the reticle to be illuminated. The condensingoptics CO form an objective lens for imaging the masking orifice, via anintermediate pupil 123, on the mask MA. A folding mirror 220 is includedfor convenient location of the illumination system in the apparatus.

According to another exemplary embodiment of the present invention, thepupil filling ratio σ may be controlled by providing adjustable,reflective coated blades in the illumination system. This exemplaryembodiment is useful in lithographic apparatus using EUV radiation asblades which absorb radiation, such as those disclosed in U.S.application Ser. No. 10/388,766, will experience a significant heat loadwhich may adversely affect the performance of the faceted mirrors usedin EUV illumination systems and other optical elements.

Referring to FIGS. 12 a and 12 b, the illumination system includes blademirrors BM selectively insertable or positionable in front of facets ofthe field faceted mirror 13. The blade mirrors BM are coated to bereflective. The coating may include a surface roughness so that thereflected radiation is scattered. Such a coating is disclosed in U.S.Pat. No. 6,927,004, incorporated herein by reference. The coating mayalso include a phase changing structure so that the reflected radiationfrom individual blade mirrors cancel each other. Such a coatingincluding a phase changing structure is disclosed in U.S. Pat. No.6,927,004.

The radiation reflected by the blade mirrors BM is directed to a beamdump BD which may be cooled to prevent adverse effects on theperformance of the apparatus.

Referring to FIGS. 13 a and 13 b, an illumination system according toanother exemplary embodiment of the present invention includes blademirrors BM selectively insertable or positionable in front of facets ofthe pupil faceted mirror 14. The blade mirrors BM are coated so as to bereflective. The coating may include a surface roughness such that thereflected radiation is scattered or may include a phase changingstructure so that the reflected radiation from individual blade mirrorscancel each other, as discussed above. The radiation reflected by theblade mirrors BM is directed to a beam dump BD which may be cooled toprevent adverse effects on the performance of the apparatus. As thepupil facets are smaller than the field facets, the pupil spotsreflected by the blade mirrors of FIGS. 13 a and 13 b are smaller thanthe field facets reflected by the blade mirrors of FIGS. 12 a and 12 b,thus a smaller beam dump may be used.

Although the embodiments shown in FIGS. 12 a and 12 b and 13 a and 13 bdescribe the blade mirrors as inserted or positioned in front of thefield faceted mirror and the pupil faceted mirror, respectively, itshould be appreciated that blade mirrors may be placed in front of boththe field faceted mirror and the pupil faceted mirror. It should also beappreciated that the various exemplary embodiments may be used incombination. For example, the devices shown in FIGS. 3 a-6, 8 and 11 maybe used in combination with the embodiments shown in FIGS. 12 a-13 a.

As shown in FIG. 15, the illumination system includes a field facetedmirror 210 having a plurality of facets 211 which receive radiation fromthe radiation source LA and form a plurality of images of the source LAon corresponding facets of pupil faceted mirror 220. The pupil facets221, with the remainder of the illumination system IL, redirect theradiation such that the images of the field facets 211 overlap on themask MA. The shape of the field facets 211 largely define the shape ofthe illumination field on the mask MA.

To control the illumination settings for illuminating the mask MA, afacet mask 222-225 is provided. The facet mask 222-225 includes apartially-opaque masking blade 222 and a solid masking blade 224connected to respective actuators 223 and 225 so as to be selectivelyand incrementally closeable into the beam PB in front of respectivefacets of the pupil facets 211. Because the image in the pupil of theprojection system PL is an image of the pupil faceted mirror 220 (theyare in conjugate planes), selectively obscuring the outermost pupilfacets 221 allows control over a, the ratio of the amount of theprojection system pupil that is filled, if no diffraction (at the mask)were present. Obscuring the outermost facets reduces σ.

The facet mask 222-225 and its operation is shown in greater detail inFIGS. 16 to 19. Although in these figures the partially-opaque maskingblade 222 is shown as solid, it include a large a number of aperturesand opaque areas as possible subject to the constraint that the size andspacing of the apertures and opaque areas must be large compared to thewavelength of the beam so that diffraction does not occur and topractical considerations of manufacture. The opaque areas preferablyhave a total area sufficient to reduce by a predetermined fraction,preferably 50%, the radiation reflected by the pupil facet. It will beappreciated that since the beam PB is not incident on the pupil mirror220 exactly normally, if the facet mask 222-225 is at all spaced fromthe pupil mirror 220, the total opaque area of the partially-opaquemasking blade 222 as a fraction of the area of one of the facets will bea little less than the predetermined fraction of the beam PB that is tobe absorbed.

As can be seen in FIG. 16, the pupil facets 221 are square and arrangedin columns. Accordingly, the partially-opaque and solid masking blades222 and 224 are constructed as a plurality of fingers 226 and 227, oneof each per column of pupil facets 221, that are selectively andincrementally extendible to cover ones of the pupil facets 221.Preferably, independent control of each of the fingers 226 and 227 isprovided to enable greater flexibility of the illumination settings,however in some circumstances pairs or groups of fingers may be groupedtogether.

The partially-opaque masking fingers 226 may be constructed, forexample, as a grid of rods, bars or wires or by forming apertures in asuitable pattern in a solid plate. A partially opaque masking finger 226formed with a plurality of rods 229 is shown in FIG. 20.

In general, for other shapes and arrangements of pupil facets, themasking blades 222 and 224 may be arranged differently. For example, forpupil facets 221 arranged in concentric rings, the masking blades 222and 224 may take the form of iris diaphragms. As an alternative toadjustable blades, it is possible to provide a plurality of blades,opaque and partially opaque, corresponding to the desired illuminationsettings and selectively interpose these into the beam as desired. Suchfixed blades may be formed as plates with appropriate openings andpartially opaque (apertured) areas and may be held in a magazine orcarousel to be inserted into the beam.

FIG. 16 shows the facet mask 222-225 in its neutral position, with bothmasking blades 222 and 224 (fingers 226 and 227) open leaving the pupilfacets 221 clear. This setting provides the greatest σ. To reduce σ bythe smallest amount, effectively a half step, the partially-opaquefingers 226 are extended one step so that the outermost ring of pupilfacets 221 a is covered, as shown in FIG. 17. The solid fingers 227remain fully retracted and the inner pupil facets 221 b are uncovered.To reduce σ further, the solid fingers 227 are extended one step, fullyobscuring the outermost ring of pupil facets 221 a, as shown in FIG. 18.Again, the inner pupil facets 221 b remain uncovered. Further reductionsin σ are achieved by further extending the fingers 226 and 227,extending the solid fingers 227 reduces σ in whole steps, whileextending the partially-opaque fingers 226 one step more provides a halfstep reduction in σ. Extending the partially-opaque fingers 226 morethan one step more than the solid fingers 227 provides an illuminationintensity distribution with a more gradual decrease towards the edge ofthe pupil. Note that to provide circular illumination modes, theoutermost fingers will move to obscure a whole column of facets whilethe central fingers advance only one facet width. When the centralfingers move a further facet inwards the next outermost column will beobscured and so on. The aim being that the area of unobscured facets isas close to circular as possible.

By providing multiple partially-opaque masking blades with differentblocking ratios, smaller increments in σ can be provided. For example,with two appropriately aligned partially-opaque masking blades, oneblocking 25% of the radiation and one blocking 50%, quarter steps can beprovided, the 25% masking blade extended one step more that the solidmasking blade provides a quarter step, the 50% masking blade extendedone step more gives a half step and both extended one step more gives athree quarter step.

Although the configurations illustrated are rotationally-symmetricalthis is not always required or desired. For example, an elliptical pupilconfiguration may be created by covering facets in one direction onlyand multipole configurations may be created by covering the appropriatefacets only.

In a variant of the first embodiment, four sets of facet masking bladesare used, arranged around four sides of the facet mirror. This is shownin FIG. 19 and can provide circular illumination modes with shortermovements of the fingers when the facets are arranged on a square grid.

A second embodiment of the invention is shown in FIGS. 21 and 22. Afacet mask 212, 213 (masking blade(s) 212 and actuator(s) 213) isprovided proximate the field facet mirror 210. The facet mask 212, 213may comprise a partially-opaque masking blade and a solid masking bladeas in the first embodiment or simply a solid masking blade. Placing thefacet mask at the field faceted mirror 210 rather than the pupil facetedmirror 220 can be advantageous in that the field facets 211 aregenerally larger in one direction than the pupil facets 221 so thatthere is additional room to provide the necessary mechanisms and it iseasier to construct the partially-opaque masking blades at a largerscale. However, additional advantages can be obtained if the fieldfacets 211 are arranged to fill pupil facets 221 other than those in thecorresponding location in the pupil mirror. For example, the outermostfield facets 211 a may be arranged to fill the innermost pupil facets221 b and vice versa, as shown in FIG. 21. In that case, closing thefacet mask 212, 213 to obscure the outermost field facets 211 a removesthe illumination from the innermost pupil facets 221 b, providing anannular illumination mode.

FIG. 22 shows the field facet mirror 210, which is the same as in thefirst embodiment. The field facet mirror 210 comprises a plurality offield facets 211 which are rectangular with a high aspect ratio andarranged in rows and columns. The facet mask 212, 213 can be embodied asa plurality of selectively extendible fingers as in the pupil facet maskof the first embodiment or as simple blades to mask a whole block offield facets 211 at a time.

The correspondence between the various pupil facets 221 and field facets211 can be chosen such that an area of adjacent field facets 211 onfield facet mirror 210 corresponds to a specific set of pupil facets 221on pupil facet mirror 220. For instance, area I of field facets 211 maybe chosen to correspond to a ring of pupil facets 221, area II tocorrespond to another ring of pupil facets and area III to an innercircular area of pupil facets 221. Areas I, II and III are easilyblocked by respective masking blades, whereas it might be much harder toblock only the corresponding pupil facets, enabling the selection ofdifferent σ values or annular illumination. Different arrangements ofthe correspondence between field and pupil facets can be used to provideother illumination modes, such as dipole and quadrupole configurationsand configurations that are complementary to the above configurations.

The facet mask of the first embodiment may be combined with that of thesecond embodiment to provide independent control of the inner and outerradii of an annular illumination mode (σ_(inner) and σ_(outer)).

This and other aspects are achieved according to the invention in alithographic apparatus including a radiation system having reflectiveoptical elements constructed and arranged to supply a beam of radiation,the reflective optical elements including a first faceted mirrorconstructed and arranged to generate a plurality of source images on asecond faceted mirror; a support structure constructed and arranged tosupport a patterning device, the patterning device constructed andarranged to pattern the beam according to a desired pattern; a substratetable constructed and arranged to hold a substrate; a projection systemconstructed and arranged to project the patterned beam onto a targetportion of the substrate; and a facet mask constructed and arranged toselectively mask one or more of the facets of one of the first andsecond faceted mirrors and comprising a partially-opaque masking bladeselectively interposable into the beam, the partially-opaque maskingblade having an arrangement of opaque and transparent areas having apitch sufficiently large so as to cause negligible diffraction of thebeam.

By using a partially-opaque masking blade to selectively mask one ormore facets, part of the radiation from that facet can be blockedwithout causing unacceptable inhomogeneity in the illumination of thepatterning device, irrespective of the fact that the exact location ofthe source image on the pupil facet is not known. In this way,intermediate illumination settings, between masking and not maskingwhole facets or rings of facets, can be provided.

The pitch should be small relative to the source image, so that theproportion of radiation blocked is independent of the source position,but not sufficiently small to cause diffraction of the beam. Preferably,for an apparatus using EUV as the exposure radiation, the pitch is inthe range of from 1 mm to 500 nm, dependent on the size of the facetsand the illuminated area.

The facet mask is preferably further controlled to adjust the proportionof the area of a facet that is obscured, for example by having aplurality of partially-opaque blades selectively interposable into thebeam. This enables multiple intermediate illumination settings,providing further versatility.

Preferably, the facet mask is arranged proximate the second (pupil)faceted mirror as this provides the most homogeneous illumination of thepatterning device.

A second aspect of the present invention provides a lithographicapparatus as specified in the a radiation system having reflectiveoptical elements constructed and arranged to supply a beam of radiation,the reflective optical elements including a first faceted mirrorconstructed and arranged to generate a plurality of source images on asecond faceted mirror; a support structure constructed and arranged tosupport a patterning device, the patterning device constructed andarranged to pattern the beam according to a desired pattern; a substratetable constructed and arranged to hold a substrate; a projection systemconstructed and arranged to project the patterned beam onto a targetportion of the substrate; and a facet mask constructed and arranged toselectively mask one or more of the facets of the first faceted mirror.

Since all radiation from one facet of the first (field) faceted mirroris incident on one facet of the second faceted mirror, equivalentillumination control can be achieved by selectively blocking fieldfacets as by blocking pupil facets. Normally however, it would not becontemplated to control illumination settings, such as a, at thisposition since this is not a pupil plane and so selective obscuration atthis position would be expected to cause non-uniformities in theillumination of the patterning device. However, because the field andpupil mirrors are faceted, selective masking of whole field facets canbe performed without unacceptable loss of uniformity.

The facets may be arranged so that field facets illuminate pupil facetsin different positions, for example facets near the periphery of thefield facet mirror may direct radiation to more centrally positionedfacets of the pupil facet mirror. Thus annular illumination modes may beset more easily, without partial obscuration of the outer pupil facetsand illumination modes that would require masking of inaccessible pupilfaces can be set.

Of course, the facet mask of the second aspect of the present inventionmay be the same as that of the first aspect and the two aspects may becombined to have selective masking of both field and pupil facets.Thereby, independent control of the inner and outer radii (σ_(inner) andσ_(outer)) of an annular illumination mode can be achieved.

According to a further aspect of the invention there is provided adevice manufacturing method including providing a substrate that is atleast partially covered by a layer of radiation-sensitive material;providing a beam of radiation using a radiation system having reflectiveoptical elements constructed and arranged to supply a beam of radiation,the reflective optical elements including a first faceted mirrorconstructed and arranged to generate a plurality of source images on asecond faceted mirror; using a patterning device to endow the beam witha pattern in its cross-section; projecting the patterned beam ofradiation onto a target portion of the layer of radiation-sensitivematerial; and selectively masking one or more facets of one of the firstand second faceted mirrors by selectively interposing a partially-opaquemasking blade into the beam, the partially-opaque masking blade havingan arrangement of transparent and opaque areas having a pitchsufficiently large so as to cause negligible diffraction of the beam.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. The description is not intended to limit theinvention.

1. A lithographic projection apparatus, comprising: an illuminationsystem configured to condition a beam of radiation from a radiationsource; a support structure configured to support a patterning device,the patterning device configured to pattern the beam of radiationaccording to a desired pattern; a substrate table configured to hold asubstrate; a projection system configured to project the patterned beamof radiation onto a target portion of the substrate; and a devicepositioned in a first plane intermediate a second plane conjugate to aplane of the substrate and a third plane conjugate to a pupil plane ofthe projection system, the first plane located between the radiationsource and the support, and the device comprising a blade selectivelyinsertable into the beam of radiation.
 2. The apparatus of claim 1,wherein the blade includes a solid blade and a partially opaque blade.3. The apparatus of claim 2, wherein the partially opaque bladecomprises a grid of rods, bars, or wires.
 4. The apparatus of claim 2,comprising a plurality of partially opaque blades, each partially opaqueblade having a different blocking ratio.
 5. The apparatus of claim 1,wherein the blade has a predetermined transmissibility pattern.
 6. Theapparatus of claim 5, wherein the blade is insertable into the beam ofradiation in a first direction in which the support structure and thesubstrate table are movable with respect to each other and thetransmissibility of the blade varies in a second direction perpendicularto the first direction.
 7. The apparatus of claim 1, wherein theillumination system includes a field faceted mirror and a pupil facetedmirror in order along a direction of propagation of the beam ofradiation and the device is positioned between the pupil faceted mirrorand the support structure.
 8. The apparatus of claim 7, furthercomprising a reflective blade selectively insertable into the beam ofradiation in front of a facet of the field faceted mirror, the pupilfaceted mirror, or both the field faceted mirror and the pupil facetedmirror, to reflect a portion of the beam of radiation to a beam dump. 9.The apparatus of claim 8, wherein the reflective blade includes acoating configured to scatter the portion of the beam of radiation orchange a phase of the portion of the beam of radiation.
 10. A devicemanufacturing method, comprising: using a patterning device to endow abeam of radiation from a radiation source with a pattern in itscross-section; projecting the patterned beam of radiation onto a targetportion of a layer of radiation-sensitive material at least partiallycovering a substrate using a projection system; and selectivelyinserting a blade of a plurality of blades into the beam of radiation ina first plane intermediate a second plane conjugate to a plane of thesubstrate and a third plane conjugate to a pupil plane of the projectionsystem, the first plane located between the radiation source and thepatterning device.
 11. The method of claim 10, wherein the plurality ofblades includes a solid blade and a partially opaque blade.
 12. Themethod of claim 11, wherein each partially opaque blade comprises a gridof rods, bars, or wires.
 13. The method of claim 1 1, comprising aplurality of partially opaque blades, each of the partially opaqueblades having a different blocking ratio.
 14. The method of claim 10,wherein each blade has a predetermined transmissibility pattern.
 15. Themethod of claim 14, wherein the blades are insertable into the beam ofradiation in a first direction in which the patterning device and thesubstrate are movable with respect to each other and thetransmissibility of the blades varies in a second directionperpendicular to the first direction.
 16. The method of claim 10,further comprising propagating the beam of radiation using a fieldfaceted mirror and a pupil faceted mirror in order along a direction ofpropagation of the beam of radiation and selectively inserting the bladeof the plurality of blades between the pupil faceted mirror and thepatterning device.
 17. The method of claim 16, further comprisingselectively inserting a plurality of reflective blades into the beam ofradiation in front of a facet of the field faceted mirror, the pupilfaceted mirror, or both the field faceted mirror and the pupil facetedmirror, to reflect a portion of the beam of radiation to a beam dump.18. The method of claim 17, wherein the reflective blades include acoating configured to scatter the portion of the beam of radiation orchange a phase of the portion of the beam of radiation.
 19. Alithographic projection apparatus, comprising: a radiation system havingreflective optical elements constructed and arranged to condition a beamof radiation, the reflective optical elements including a first facetedmirror constructed and arranged to generate a plurality of source imageson a second mirror; a support structure constructed and arranged tosupport a patterning device, the patterning device constructed andarranged to pattern the beam according to a desired pattern; a substratetable constructed and arranged to hold a substrate; a projection systemconstructed and arranged to project the patterned beam onto a targetportion of the substrate; and a facet mask constructed and arranged to(i) selectively mask one or more of the facets of the first facetedmirror, or (ii) selectively mask one or more of the plurality of thesource images at the second mirror, or (iii) both (i) and (ii), andcomprising a partially-opaque masking blade selectively interposableinto the beam.
 20. The apparatus of claim 19, wherein thepartially-opaque masking blade has a regular periodic arrangement ofopaque and transparent areas having a pitch sufficiently large so as tocause negligible diffraction of the beam and covering substantially anentire facet or source image respectively.
 21. The apparatus of claim20, wherein the pitch is in the range of from 1 mm to 500 nm.
 22. Theapparatus of claim 19, wherein the facets of the first faceted mirrorare arranged in lines and the partially-opaque blade comprises aplurality of partially-opaque fingers selectively extendible alongrespective lines of facets.
 23. The apparatus of claim 19, wherein thefacet mask is arranged proximate the second mirror.
 24. The apparatus ofclaim 19, wherein the facet mask further comprises a solid masking bladeselectively interposable into the beam to respectively (iv) mask one ormore of the facets of the first faceted mirror, or (v) mask one or moreof the plurality of the source images at the second mirror, or (vi) both(iv) and (vi).
 25. The apparatus of claim 19, wherein the facet mask iscontrollable to adjust the proportion of area of a facet that isobscured by the partially-opaque masking blade.
 26. The apparatus ofclaim 19, wherein the facet mask has a plurality of partially-opaquemasking blades selectively interposable into the beam.
 27. The apparatusof claim 19, wherein the second mirror is a faceted mirror.
 28. Alithographic projection apparatus, comprising: a radiation system havingreflective optical elements constructed and arranged to condition a beamof radiation, the reflective optical elements including a first facetedmirror constructed and arranged to generate a plurality of source imageson a second mirror, wherein a group of adjacent facets of the firstfaceted mirror are arranged to direct radiation to an area of the secondmirror, the area being arranged in a configuration selected from thegroup comprising: a substantially annular configuration, a multipoleconfiguration, a substantially circular configuration, and anycombination of the above configurations; a support structure constructedand arranged to support a patterning device, the patterning deviceconstructed and arranged to pattern the beam according to a desiredpattern; a substrate table constructed and arranged to hold a substrate;a projection system constructed and arranged to project the patternedbeam onto a target portion of the substrate; and a facet maskconstructed and arranged to selectively mask one or more of the facetsof the first faceted mirror.
 29. The apparatus of claim 28, wherein thesecond mirror is faceted mirror and the area comprises a set of facetsof the second faceted mirror.
 30. The apparatus of claim 28, whereinfacets near a periphery of the first faceted mirror are arranged todirect radiation to a centrally positioned area of the second mirror.31. A lithographic projection apparatus, comprising: an illuminationsystem having a plurality of mirrors; a support configured to support apatterning device, the patterning device configured to pattern the beamof radiation according to a desired pattern; a substrate tableconfigured to hold a substrate; a projection system configured toproject the patterned beam of radiation onto a target portion of thesubstrate, the projection system having a plurality of mirrors; and areflective blade selectively insertable into the beam of radiation infront of at least one of the plurality of mirrors to reflect a portionof the beam of radiation to a beam dump.
 32. The apparatus according toclaim 31, wherein the reflective blade includes a coating configured toscatter the portion of the beam of radiation or change a phase of theportion of the beam of radiation.